The invention relates to a substrate treatment installation.
If exposure or heat-treatment processes are intended to be carried out with the aid of pulsed gas discharge lamps (flash lamps) on large substrates, that is to say for example with a surface area of about 1 m2 or more, this can be achieved in two ways: one is for a single lamp (or a small array of lamps which cover only a part of the substrate) to be moved relative to the substrate so that the entire substrate can ultimately be exposed or heat-treated by combining a plurality of exposure fields. As an alternative to this, an array of lamps which extends over the entire substrate may be ignited once. There are many examples—such as photoresists to be exposed on a substrate—in which a combination of a plurality of exposure fields necessarily leads to a detrimental double exposure owing to their necessary overlap. In these cases, it is only possible to use an array of lamps which cover the entire substrate.
An air-cooled lamp array which covers all or parts of the substrate surface is prior art. In processes which can or should only take place in a vacuum, lamps are arranged outside the vacuum chamber and the substrate is exposed or heat-treated through an optical window in the wall of the vacuum chamber, through which the lamps shine into the vacuum chamber. Owing to the pressure difference between the atmospheric pressure outside the installation and the vacuum prevailing inside the installation, the optical window is therefore exposed to a force of at least 105 newtons per square meter of substrate surface. The optical window would consequently need to be made correspondingly thick—that is to say many centimeters. Apart from the high production costs of this specially manufactured glass (typically quartz glass owing to the high transparency in the UV range), a significant part of the light from the lamp is absorbed in the glass of the optical window owing to the large thickness of the glass, in order to achieve the required strength.
In the case of lasers which are used for boring turbine blades, for example, a 200 mm long gas discharge lamp is used as the light source. Owing to the high flash frequency, for example 500 pulses per second, i.e. a relatively high average electrical power of for example 8 kW, the lamp needs to be water-cooled. The cooling is generally carried out by a so-called flow tube, in which the lamp is embedded. The flow tube is a quartz glass tube, through which deionized cooling water flows and therefore cools the lamp. Flow tubes permit turbulence-free water flow along the lamp.
US 2002/0148824 A1 proposes a system for the thermal treatment of surfaces of semiconductors, these being heated by thermal radiation generated by heating lamps. The lamps are in this case surrounded individually or in groups by locally transparent housings in order to isolate them from the ambient conditions of the treatment chamber, and optionally to cool them with suitable gaseous or liquid media. In addition, thin quartz glass sheets may also be arranged between the housings comprising the lamps and the surface to be thermally treated.
Similarly, US 2007/0095289 A1 discloses a heating device which can likewise be used for the thermal treatment of surfaces of semiconductors. The heating unit itself in this case consists of a bent quartz glass tube through which a carbon wire is fed, which, when an electrical current flows through it, generates heat and imparts it to the surface to be treated. The quartz tube is in this case mounted firmly on a reflector plate and is covered by a protective cover member consisting of silicon carbide.
It is an object of the present invention to improve known substrate treatment installations in such a way that substrates can be treated therein by light without cost-intensive optical windows with high weight being required.